Mud scraping device



July 21, 1942 w. w. HARTMAN E-rAL 2,290,429

MUD SCRAPING DEVICE original Filed March 7.21940 05597 MMA/m5@ W/a/AM 'ATToRNEx y Patented July 2l, 1942 2,290,429 MUD scRAPiNo DEVICE William Water Hartman and Robert Alexander teps, Los Angeles, Calif.

substituted for abandoned application Serial No.

322,724, March 7,

1940. This application November 30, 1940, Serial No. 368,094 6 Claims. (Cl. 166-18) This invention relates to mud removing mechanism for use ln wells during the drilling and casing thereof, and especially during proper preparation of the well hole for effecting a cement job therein.

The present application is a substitute for application Serial Number 322,724, filed March 7, 1940, and which became abandoned on November 17,1940. n

In drilling wells according to the rotary system, it is customary to circulate heavy mud down through the drill stem and up through the Well hole, the benefits of this mud circulation being well known and unnecessary to describe here. However, owing to the great hydrostatic pressure which this mud column sets up in deep wells against the open walls thereof, and because oi a certain porosity ofthe earth formation comprising these walls, the water component of this mud tends to leak or filter out into the formation, and as this occurs the fine particles in the mud tend to Ybuild up a mud cake or wall that might be likened to a lter cake plastered around the walls of the well'hole and making the bore of the well hole somewhat smaller than the original drilled diameter thereof by the thickness of this mud cake. Naturally this mud cake will tend to be thicker where the earth formation is very porous, and it is probably entirely absent or negligible Where the earth formation is impervious to water filtration. V

When such drilling of the well has' proceeded to a certain depth determined by considerations that need not be discussed here, it is customary to install pipe or casing in the well to that depth, and by well known processes to then force a cement column up in the space between this casing and the well hole, such column of cement being often a few hundred feet high and extending from the bottom of the casing upward. The purpose of this cement column is to positively seal off the entire space between the casing and the walls of the hole, to prevent flow of water or other undesirable materials from the upper part of the well downward along the outside of this pipe or casing into the lower parts of the well where the oil, gas, or other desired products are produced by the well. The effectiveness of this cementing operation, as a seal against contamination, is a very important consideration in the successful completion of wells.

In connection with such cementing it is apparent that the possible presence of mud cake as above described, covering the earth formation in the well hole, may prevent the cement which can be used from setting directly. against vthis earth formation. Furthermore, this mud cake may sometimes be of character to impair the ability of the cement to correctly perform its sealing action as above described, and in general it is deemed advantageous to have the cement fill the entire space and make good bond between the earth formation and the steel casing to insure a perfect seal. This is 'notso certain if a mud cake intervenes betweenfth'e cement and the earth formation. i

Itis an object of this invention to provide simple, dependable and efcient instrumentalities in the Well hole to remove the mud cake from the well bore or -,hole Where desired, so that the cement may make direct bond with the formation and completely ll the space between the casing andthe formation." r

It is another object of this invention to provide simple, dependable and.'efficient instrumen-v talities whereby little or no mud cake is removed from the wall ofthe W`ell\bore-while the' device is being lowered into the well, but whereby'the mud cake is efficiently and completelyremoved from the wall of the Well while the device* is being moved upward through the Well;` v

While certain parts and features of our invention are themselves noyel, and may be used either with a centralizing guide or separately therefrom as desired, nevertheless it is a further object oi our invention, when same is constructparts and features with ing guide so that our invention makes possible the combined benefits of properly removing mud from the formation wall, so the cement will make and also properly centralizing the pipe or casing in column will be of uniform thickness around the casing, in order through both these advantages to give best assurance of a successful cementing Other objects, benefits and advantages of our invention will become apparent from consideration of the following description, also of the appended claims and the drawing.

In this specification we will disclose our invention in its at present preferred form, together with certain modifications thereof, but we do not limit ourselves to this form or tothe particular modifications disclosed, because various further changes, modifications and adaptations can be made in this invention Without departing'rom the essence or scope thereof as expressed in the appended claims. l.tlsofcrain objects, advanthe hole so that the cement tages *and benets of this invention will be apparent to those skilled in the art, and the same lare included within the scope of this invention even designated by like reference numerals.

Fig. 1 is an elevation of the well hole, partly in section, showing one form of mechanism embracing our invention, located therein.

Fig. 2 is an enlarged transverse section taken on line X11-X2 of Fig. 1 looking in the direction of the arrows.

Fig. 3 is an enlarged elevation view of a portion of a spring with a mud removing member thereon, this view being procured by looking at these parts in Fig. 1 from the inside outward mounted on the spr Fig. 5 is a sectional view of the mud scraping member alone, taken along line X5X5 of Fig. 3,

. looking in the direction of the arrows.

a sense forming a part thereof, 'is shown a layer of mud cake 3 formed thereon in manner already described.

In the upper portion of Fig. 1 is paratively large sized well casing or pipe 4 alaround this casing 4 is shown cement 6 completely filling the space between the outer surface'of the casing and the cement job.

Through the drilled hole l and through the already installed casing 4, the somewhat smaller pipe or casing 8 is shown in the course of being lowered from the surface of .the earth to the bottom of the drilled hole I, and when landed at the bottom this casing 8 will presumably be cemented in place there in approximately the manner that the larger casing 4 is shown landed and cemented in the well hole 1.

On the pipe or casing 8 is shown our preferred form of mud remover, or mud scraping device, the same being in this instance combined to function also as a pipe or casing centralizar in the well hole, as will later be more particularly described.

Essentially our invention consists in the out- Wardly Viewing these mud scraping parts wall is more certain, positive and dependable.

Also, it is apparent that the laterally extending mud scraping parts I0 could readily be formed or fashioned as an in the drawing, -but before discussing this furthese advantages and we will rst describe is followed more or less genther, and in order to make improvements more clear, a procedure which erally during the lowering and setting of the casing 8 in the well.

During such lowering of the pipe or casing it is understood that there is no mud circulation, i. e. no mud is being :pumped down through this casing and up from the bottom thereof through the well hole, the absence of circulation at this time being due to pipe 8 being floated in. However, when pipe 8 reaches the bottom of the hole, and in preparation for the introduction of the cement, circulation down through this pipe and up through the well bore outside the pipe is set up, the object being to clarify the mud then in the well hole by replacing it either with comparatively light mud, or even with practically clear water, so that when the cement is introduced it will be set in almost clear water at the bottom of the hole. The reason for this is that cement sets up stronger and better in water that is clear or reasonably clear, than it does in heavy mud. During this portion of the circulation some of the mud cake 3 will no doubt be washed off the sides of the hole, but it is reasonable to suppose that va portion of the mud cake remains thereon. Furthermore, during the circulation just referred to, the pipe 8 is slowly raised and lowered in the well as an aid to circulation and for the purpose of keeping the pipe free against any tendency of the formation to cave and seize the pipe. Ordinarily the distance traversed during this up and down movement is rather limited in extent. It is during the upward portion of this up and down movement of the pipe that the -most effective scraping of mud cake from the walls of the well is procured by our at 'present preferred form of our invention as illustrated in the figures. In this connection we desire to point out that in this form of our device featuresare intentionally included to provide that during the lowering of pipe 8 through the open well hole, which may be a few thousand feet.in depth or more, the members I should scrape or remove as little mud as possible from the walls of the hole. The reason is that if these members scraped the mud olf all the way down along thousands of feet of open hole, there might then be such an accumulation of mud in the bottom of the hole as to make it diliicult to carry pipe 8 to the bottom of the hole, and another objection is that there may be places along the formation where it is not desirable to remove the mud as this might ,promote caving of the walls if the`supporting power of the mud cake were removed. In short there are cases where it is desired to run the mud remover to the bottom of the hole with minimum disturbance of the mud during descent, and to meet these requirements we form parts l0 and position them on the springs so thatl the upper portion, say from a to b, or c, in Fig. 3, lies approximately at the peak p, Fig. 1, of the spring 9, i. e. approximately at the place where the spring is bowed outwardly the furthest, or in any event, we form and position these upper edges I4 of members I0 so as to insure that they bear rmly against and engage the mud cake and well wall under the expansive [force of springs B to thereby scrape or remove the mud cake from the wall of the well hole during any upward movement of the device through the well. At the same time the lower portion or edges l5 of the blades or members i0, say from 'point d toward the lower end e thereof, see Figs. l, 2, 3, 5, 7 and 8, gradually recede from the mud cake and well wall toward the axis of center of the device, to thereby normally clear the well wall, so that during descent through the well the lower portion off this member I0 acts more or less like a sled runner to not cut the mud from the well wall but rather to glide over and compress it with relatively little disturbance of the mud during descent, or at least less disturbance and removal of the mud from the wall of the well hole during descent than during ascent of the device. Reference to the sectional view of member l0 as shown in Fig. 5

illustrates in magnied form this receding of the lower portion of the mud removing part l0 from the well wall by showing the lower portion l2 thereof as warped inward as it approaches its bottom contour f, see Fig. 5 in connection with Figs. 1, 2, 3, 7 and 8. Therefore, by thus forming and bringing the lower portion and edges I5 of members I0 in closer to the center or axis of the device than the upper edges I4, as just indicated, it is apparent'that the lower portion and edges of the parts or members I0 will tend to clear the mud cake and well wall and will more or less slide or trowel over the mud 3 and compress it during descent, rather than to lcut it away from the wall at this time.

However, during ascent of blades I0 through the hole there is no such troweling action and the upper edges I4 of members I0, being pressed by the springs hard against the loose soft mud will tend to plow into this mud cake and remove or scrape it fromthe well hole during the upward motion of pipe 8 in the well. However,

since circulation upward through the well has been started just prior to this and is proceeding at this time, the mud scraped from the well wall will be oated or washed upward and discharged from the well at the surface of the earth, and'there is no risk of clogging the well or sticking the We consider this improvement whereby the device can be run down with minimum mud scraping, but whereby efficient scraping and mud removal occurs during the up stroke-ofthe pipe and device, as a desirable and important feature of the invention. v

A further feature of improvement to which we wish to call attention is the fact that the upper scraping edges I4 of members l0 diverge from each other as they sweep laterally outward and downward from each side of spring 9, i. e. the portion of these edges between a and b", Fig. 3, diverge from each other as just stated, the object and advantage being twofold, first, to cut or scrape the mud from the well wall with a clean shearing action, and second, to insure that these blades l0 will freely and automatically collapse inward toward thev body of pipe 9 when the springs 9 are pulled upward through'any restriction in the hole, as for instance if it should be necessary to pull the device up into casing 4 through the bottom opening thereof at 5, see Fig. 1. That is, the sloping divergence of edges I4 will permit member I0 to enter opening-5 easily, and to this end it is'essential that both edges should slope and diverge on eachl side of the spring 9. Another important advantage in having these upper scraping 'edges I4 of member I0 diverge out and downwardly on both sides of spring 9, is that while the scraping action is occurring, during the upward movement of the device, the downwardly directed scraping resistance on one side of the blade and spring 9, will to a considerable degree balance the like resistance on the other side of the blade and spring 9, so that the action will therefore tend to be balanced and to stabilize the spring 9 and thus the entire device willvbe more durable and dependable than if the scraping edge swept out and` downward from one side of the spring only.

Likewise we prefer that the lower edges I5 of members I0,`should diverge from each other as they pass laterally outward and upward from the spring. Such divergence of lower edges I 5 of member I0 also aids this member in nicely collapsing in unison with spring 9 toward the body of the pipe if the springs must be pulled downward through any undue restriction as indicated at I6, Fig. 1, and as may occasionally occur through intrusion of a boulder, or partial collapsel or settling of the formation, or other varied causes.

A further feature of improvement has for its object that members I0 will not interfere at all, or only slightly, with the general flexibility of the. bowed springs 9. It will begapparent that if this scraping member I0 were fastened to the spring along the entire upright length of member I0, the latter would add considerable stilness to spring 9, especially in the area covered by member I 0, and the bending of the spring would consequently not be uniform along its length. vTo prevent this we secure only the upper portion. of the rscraping member I0 to theY spring, this vbeing effected by welding the two members together through holes Il formed in blade IIJ, and also by depositing welding metal Iii-along the upper edge of blade IU where it overlaps the spring 9. Incidentally, this welding metal I8 is tapered off gradually from the outer surface of member I0 down to the level of the outer surface of spring 9 so that there will be a wedge or tapered effect there, and not a sharp shoulder, whereby the spring and blade will nicely enter any restriction such as the bottom of casing 4, at point 5, or any other restriction that may be encountered, and also during scraping this part of the blade which passes entirely across the outside of the spring, and the .welding metal there located, will scape away and wedge out the mud in the area under or in front of the springs. By means of the welding metal applied at I8 and also at holes I 'I as just indicated, the scraping blade I0 is securely attached to spring 9, but only in vicinity of the upper portion of this member. Below the lower hole I1 we prefer'to leave this member I0 unattached to the spring in any positive sense, i. e. we prefer to leave the lower portion of member I0 free to slide downward over the outer surface of spring 9 so that if the spring is pressed or flattened down to practically touch pipe 8, as in passing any severe restriction, the member I0 will not interfere with the bending or attening of the sprlng, nor with its subsequent expansion, because this lower portion of member I0 is free'ly slidable over the surface of the spring. and does not restrict or cramp the spring. Although the lower end of member I0 is thus slidably free on the spring, we prefer that it should be guided thereon, and this we effect by forming the ears 20 of the scraper blank, see Fig. 4, to embrace the spring and we then weld the adjoining edges 2I thereof together on the inside of the spring as shown in' Fig. 3. To prevent this lower portion of the scraper Vmember I0 from stripping upward and buckling off the spring due to friction during descent through any extreme or severe restriction in the hole, we sometimes provide a stop,

which may be in the form of member 22 welded to spring 9 through hole 23 and also at 24, see Fig. 3, this stop co-acting with the upper edge of ears 20 of member I0 to keep the latter from l buckling or stripping upward under the circumif the lower end of member I0 can slide downward along the spring.

'In Fig. 2 the mud scraping members I Il overlap each other at their lateral extremities II, between the springs lEl, and in this gure the overlappingv is seen to proceed around the device by having the left end of one blade lying on the inside of its neighbor while the right end thereof is on the outside of the other neighbor, this sequence being consistent and continuous around the device. This arrangement has the advantage that it can be consistently applied around the entire device irrespective of whether the num ber of springs be even or odd. In Fig, 7 the overlapping arrangement is slightly different, the alternate members |01 overlapping each other by having both of the lateral extremities of one of them lying outside of both neighbors, while both lateral extremities of each of these neighbors lie inside of theirl respective neighbors, and so on around the device. This arrangement is perhaps slightly smoother in appearance than that shown in Fig. 2, but it can only be applied consistently around the entire device when the number of springs is even. In any event by having the adjacent lateral extremities of the neighboring mud scraping parts overlap by lying inside and outside of each other, the helpful operating result is achieved that as this entire scraping device compresses and expands radially in passing down through the various variable bores of the well, for instance in passing from the smaller casing 4, into the larger open hole below it (see Fig. 1), the mud scraping parts will freely slide over each other laterally without danger of their adjacent extremities jamming against and injuring each other.

Fig. 8 illustrates another modification wherein the novel scraping blades arev not arranged in a continuous ring around the device as in Fig. 1, but are arranged in staggered elevation as shown. In Fig. 8 the blades are designated by reference numeral |02, and the springs as 92.

While certain modifications have been specifically illustrated in Figs. 7 and 8 it is understood that this is not intended to exclude other changes and modifications, many of which can be made without departing from the spirit of our invention.

It has been previously indicated that in accordance with the broader aspect of this invention the mode of mounting the springs 9, with their scraper blades I0, on pipe 8, can be effected in any suitable or desired manner whatsoever, but we prefer to mount them in a certain way as follows:

The ends 25 of the springs 9 are located in slots 2E cut into the substantially cylindrical collars 21, and the spring ends are securely welded to these collars in the slots 26 by depositing welding material 28 along the edges where the springs adjoin the slots. This can be best understood from Figs. 1 and 6. The springs are bowed outw-Y wardly from their ends V25, and this bowing proceeds in such manner', as best seen in Fig. 6, that, ,when the spring passes over the end 29 of the collar 21, the' inside surface of the spring is ent vtirely clear of the slot 25, which in effect creates a series of iingers 3B between the springs. These fingers point downward in the upper collarV 21, and point upward in the lower collar 21, `and in each collar these ngers form an abutting shoulder noticed at 29 in Fig. 6. Except for acertain limitation of movement which we will describein a moment, we prefer to make both collars 21 of such internal diameter Ythat they 4will slide lengthwise on the pipe 8 and also rotate thereon if necessary.` In fact, in this preferred form of the invention, since all the springs 9 have their respective ends welded to the spaced collarsy 21, it

is apparent Vthat a unit is formed comprising these collarsV 21, the loutwardly bowed springs 9A and the scraper blades l0, and this unit excepting certain limitations that we will describe in a moment, is preferably free to slide lengthwise and to rotate on pipe B. however isY limited by a stop secured to pipe 8 between the upper and lower collars 21, this stop in'Fig; 1 being in the forrnof two separate stoprings 3l and 32,1l the important feature of the stop shoulder 3d comprising the lower edge of the lower ring 32. The upper stop 'shouldert Vis The lengthwise sliding -stop being that there is an upper shoulder 33 comprising the upper edge of ring 3 l and a lower adapted to butt squarely against the bottomfa'ce 1' `or shoulder 29 of the butting fingers 39 vof the Yupper collar 21, and similarly the lower stop shoulder 34 is adapted to buttsquarely against the bottom face or shoulder 291 of theiingers 31 of the lower collar 21. The stop rings 3l and 32- being securely attached to the pipe by weldrin-g deposited in holes 35, it is apparent that the stop shoulders 33 and 34 on these rings are oprie- Jil tive abutments carried rigidly on the pipe adapted to butt against the corresponding shoul@ `ders ofthe collars 21 in ths normal position ci the latter and without any lost motion between them. By mounting the stop between collars'll the following important advantager is procured, especially when the pipe is either raised or low'- ered through any restriction inthe hole.KV If such restriction is to be passed during descent, the

cutting Vshoulder 34 on lower stop" ring '32 will V butt downward a-gainst faces 291 of the butting ngers 361 of collar 21, and the springs @being be pulled downward through the restriction.' By

Vthus pulling the springs downward through such restriction, instead of pushing them through it from above, the springs will fold rin nicely against the pipe without buckling or breaking `oihand furthermore because of the downwardlyjconverging edges or sides l5 of the scraper blades LG, these blades will also fold in and be drawn nicely through any such restriction. This inward folding of members l@ will occur along their width,y that is their radius of curvature as viewed in Figs.`

' fastened to this collark at 'their lower edges will 2 and 7 will be reduced, this being eiected by action of the downwardly converging edges I5' of blades itl which will tend to bow and'draw these blades laterally inward asrthe'y are pulled and drawn through into the restriction. In this action the stops '26, vattached to springs 9, and

abutting parts 29V of members lll,- cooperate as already indicated. Conversely if pipe is raised through any restriction in the hole, as for instance if it should be necessary to raise it sutilclently to pull our device up into casing 4 through Ythe bottom opening thereof at 5 in Fig. l, it'is' apparent that the upper shoulder 33 of the upper` stop ring 3l, would butt against lower face 29 of Y butting fingers 30 of upper collar 21, see Fig. l,

and the'upward movement of pipe Brwould therefore pull springs 9 upward from their upper ends intoA casing ,V and by thus pulling vinstead of pushing the springs into the restriction it is apparent that springs 9 would not buckle but would readily fold inward toward pipe 8 and pass freely into and through therestrictionand casing 4,'

and this inward folding would apply also to the scraper blades l0 especially because of the downwardly and outwardly diverging character -of upper edges I4 thereof. Because of this converg-k ence these blades I0 tend to bend laterally inf .ward as theyare drawnlupward into'a restriction, i. e., their radius of curvature as viewed inAAV Fig. 2 would become smaller. as blades I0 are drawninto such restriction, Vthis being expedited and in fact more or less compelled by the upward Y convergence of the edges I4. Also the welding I8 at the top of blades. I9, being tapered or beveled: inward as already described, .would also pass `freely upward into andthrough any restriction,

as such beveling avoids square shoulders that might hook on. Thus, inthe preferred form of our invention asllllustratedfin Fig. 1 the outwardly bowed springs, with scraper blades lil thereon, would freely and safely pass any restriction whether pipe 8y ismoved upward or .downward therethrough, [and this smooth passagejin either directionis promoted by thecooperative'aotion of the stop `mounted on the pipe n between collars 21, and theupward convergence, of upper edges l@ of members IG, and also the downward convergence of the loweredges I5 of members lll. These edges need not be a straightVV line asshownV at thelupper edges I nor need they be curved as shown by the lower edges 45 it being apparent that vthe upper and loweredges of members Ill can both be straight,or they vcan both be curved, as desired, and the curve can V take various forms'ofV divergence as desired.

VWe might add` that in order to promote free Y passage of blades le downward through restricu tions, these blades are beveled or tapered down wardly at their extrem-e lower edges ,38, seeFig. l, but even if they were not sobeveled the obstructing shoulder at this ppint wouidnot ordinarily be -v as lar'geas indicated in the drawing.because1we preferthat the thickness Vof the material of whichV members@ are made should be less thanfshown,

, this thickness having been exaggerated in theV n' gures topermit Aillustration thereof. K

VWith reference to Figs. 3, 4 and 5 1 we scraping action of these members I9. Y However,

since the thickness of members vlllis lessfthan that' indicated in the' drawing, the mud scrapingY factorily l edges thereof will function quite vsatis whether they aresharpened or not. A

f From the foregoing descriptionit.isbelievedf that the construction and operation of ourmech-,

anism will be readily understood.

Tosummarlze the operation briey, itjisun-rVV i derstood thatfas our mechanism is moved upwardI`V Y VVthrough the well-lole the laterally extending mud scraping' members kwill remove and'clean the mud from the walls. The mud thus removed mehr further add that we prefer to sharpen the upper, 1 edges lof the scraper'bladesflby lieveling theseA edges upwardv andA outward as shown, in f these figures, especially'between-,points and bf Fig. 3. IThis sharpening improves,` the mud fluid circulation occurring at this stage of the operation.

'Ihe formation being scraped clean of mud by r action of our device, and the springs 9 functionlng also as a centralizer -to hold pipe 8 central in the hole, the cement can then be pumped into place in Well known manner with the assurance that when the cement is set it will completely lill the space between the pipe and the earth formation proper, and make good bond at all points because of the removal of deleterious mud, and in addition the cement plug thus formed will be of uniform thickness all around the centralized pipe. Such a cementing jobgives every assur' ance of effecting an ellicient, successful seal in accordance with the vwell known robjects of cementing; The advantages of rfreely and safely moving our device either upwards or downwards through any restrictions in the well bore, without risk of injuring either the device or the well, have already been described in detail.

While we have shown the sprin-gs 9 as of flat rectangular cross section, they may of course be.

of round, square or other cross section as desired or to suit special requirements or inodil'ica-v where the spring is bowed outwardly to approxi imately its maximum distance from the axis of the device, and the upper edge of each such blade I being adapted to engage the wall of the well hole to scrape mud therefrom, and the lower part of each such blade being bowed inwardly torrecede from the wall of the well hole toward the center of the device, the lower end of each such blade being free to sli'de lengthwise of the spring, and a stop means for limiting the upward movement of the lower end ofthe scraping blade along the Spring.Y

2. In a device for scraping mud from the wall of a well, the combination .of outwardly bent springs spaced apart fwrom each other circularly around the axis of the device, and mud scraping parts associat'ed'with said the adjacent lateral extremities of the neighbor-V ing mud scraping parts overlap each other by lying insideand outsidewof each other, so that as springs and` extending laterally thereof in curved direction to conform,

said device compresses and expands radially in passing'through variablebores of the well said mud scraping parts will 'freely slide over each other laterally without interference between their adjacent extremities. Y

Y 3. In a device for scrapingmudi'rom the'wall of a well, the combination Loffoutwardly bent springs spaced apart from' eachlothercircularly around the axis of the device, and metallic mud scraping blades' attached to said springs and presenting atl approximately the saine elevation on both sides of each spring upper mud scraping portions that are curved laterally to 'conformvapproximately with and contact u the circular Wall ,of the well, and the metal comprising the lower portions` of all such blades being bent lnwardto- 2,290,429 `floats up and out of the well by virtue of theV ward the axis of the device to bring such lower portions of all the blades nearer the axis of the device than the 'said upper mud scraping portions thereof, so that said blades willY scrape mud from the wall of the well during the upward movement Y of the device but ,will tend to glide over and scrape lime or no mud from the wall of the wen during the downward movement of the device through the well.

4. In a device for scraping mud from the wall a well, the combination of outwardly bent springs spaced apart from each other circularly around the axis ofthe device, and metallic mudY device to bring such lower portions `of all the blades nearer the axis of the device than the said upper mud scraping edges thereof, so that said blades will scrape mud from the wall ofthe well i during the upward movement of the device but will tend to glide over and scrape little or no mud from the wall of the well' during the downward movement of the device through the well.

5. In a device for scraping mud from the wall of anwell, the combination of outwardly bent springs spaced a'part from each other circularly around the axis of the device, and metallic mud scraping blades attached such mud scraping blade presenting an upper mud scraping portion-that passes entirely across the outside of its spring and then extends laterally'on both sides of its spring in curved direction to conform approximately with and contact the circular Wallof thewell, and the metal comprising'the lower portions of all such blades being bent inward toward the axis ofthe device to bring'such lower portions of the blades nearer the axis of the device than the said upper mud scraping portionsthereof, soA that said blades will duringfthe upward movement of the device scrape'mud from the wall of thewell including all the area in front of the springs, but will tend to glide'over and scrape little or no mud from the Wall ofthe well during the of the device through the well.-

6. In a device for scraping mud from the wall of a well, the combination of outwardly bowed springs spaced apart from each other circularly around the axis of the device, and mud scraping blades mountec on the springs and presenting upper laterallyextending mud scraping edges, the said blades being so located Y'on the springs that said mud scraping edges :are approximately at the places where the springs are bowed 'outward to their maximum amount from the axis 'of the device, means for securely fastening the said blades to their respectivesprings at the upper partsl of saidY blades, and the lower parts of said blades being slidably secured to their respective springs at places on thesprings substantially to said springs, veach a below the places where the blades are securely fastened to their respective springs, so that the said lowerparts Vof theV blades will slide along the springs when'the springs ex;

WILLIAM WALTERHARTMAN. ROBERT ALEXANDER STEPS.

downward Imovement 

